U.S. energy firms cut oil rigs for a fourth week in a row this week, data showed on Friday, a sign the continued weak prices were causing energy firms to reduce drilling plans.

Drillers removed four oil rigs in the week ended Sept. 25, bringing the total rig count down to 640, the lowest since July, after cutting a total of 31 rigs over the three prior weeks, oil services company Baker Hughes Inc said in its closely followed report.

That compared with 1,592 oil rigs in the same week a year ago and an all-time high of 1,609 in October 2014.

The reductions over the past few weeks have cut into the 47 oil rigs that energy firms added in July and August after some drillers followed through on plans to add rigs announced in May and June when U.S. crude futures averaged $60 a barrel.

U.S. oil futures this week however were averaging $45 a barrel for a third week in a row, near the lowest levels for the year on continued lackluster global demand and lingering oversupply concerns.

Earlier on Friday, U.S. crude prices were up around 2 percent along with gains in Wall Street stock markets on stronger revised U.S. economic data.

Despite the short-term price gain on Friday, U.S. oil production has declined over the past several weeks due to the weak crude market.

U.S. oil output last week held around 9.1 million barrels per day (bpd) for a third week in a row, according to government data. That was down from average production of 9.6 million bpd from late May to mid-July, which was the highest output since the early 1970s.

"The current rig count is pointing to U.S. production declining sequentially between the second quarter and the fourth quarter of 2015 by 255 thousand barrels a day," analysts at Goldman Sachs said in a note.

Goldman however expects production to resume growth in 2016 by 70 thousand bpd. That however was down from the bank's forecast last week for 2016 growth of 110 thousand bpd due in part to continuing declines in the oil rig count. (Reporting by Scott DiSavino